The mast cells of the gastrointestinal tract have long been thought to play an important role in many inflammatory processes of the bowel, including parasitic infection, inflammatory bowel disease and, more obviously, gastrointestinal allergy. Using isolated mucosal mast cells, we will focus on the secretion of pro-inflammatory products -- histamine, leukotriene, prostaglandins and other products of arachidonic acid metabolism -- which have been implicated in the inflammatory process in gut and in other tissues. By using mechanical and enzymatic dispersion, we will obtain a single cell suspension containing mucosal mast cells from intestinal mucosa. Using IgE mediated and other stimuli such as compound 48/80, calcium ionophore, and D2O we will assay the secretion of mediators from this cell preparation. We will address the question of mast cell heterogeneity by comparing these responses with those of human lung mast cells when stimulated by a similar variety of secretagogues. This will include examining the effect of gastrointestinal hormones such as gastrin, VIP, and secretin. These cells will also be compared as to the inflammatory products secreted, concentrating on the metabolites of arachidonate metabolism -- prostaglandins and leukotrienes -- which will be assayed with radioimmunoassay and high performance liquid chromatography. We will examine the action of known inhibitors of secretion in lung mast cells on mucosal mast cells, and will also test pharmacologic agents used in treatment of intestinal conditions such as inflammatory bowel disease. Results obtained with the mast cell suspension will be corroborated using chopped mucosal tissue and cells obtained after mechanical treatment. After initial determination of the type and pattern of mediator release of the mast cells in suspension, we will purify these cells using techniques developed for purification of the human lung mast cell. With the highly enriched cells, we will confirm the observations made with the crude suspension. We can then study the details of mechanism of mediator release, the arachidonic acid metabolism, proteolytic enzymes produced, and the nature of the proteoglycans in the context of similar studies which are being carried out with human lung mast cells. We will then be able to assess whether there is in man, as in the rodent, mast cell heterogeneity. Further, we will have a beginning knowledge of the mechanism of mediator release and its pharmacologic control in a cell which contributes to gastrointestinal allergy and inflammatory processes.